Obsessive-compulsive disorder has been studied from several different perspectives since the beginning of this project in 1980. During the past year, three areas of interest have been pursued. We have followed up on our previous treatment studies with a double-blind comparison of the tricyclic antidepressants clomipramine and desipramine. Clomipramine appears to be more effective than desipramine for reducing obsessional symptoms, although the drugs have been previously shown to be equally effective as antidepressants. A second research focus has looked at cerebral blood flow during laboratory precipitated anxiety in obsessive-compulsive disorder patients. Results from this study are currently being analyzed. Finally, the natural course of this disorder has been investigated with a follow-up study of subjects recruited in 1980 and 1981.